If, for example, a draw texturing machine is used to process yarn at high temperature, the temperature of the heater is set so that yarn at the heater's outlet will be at the required temperature. With polyester yarn, for example, the temperature at the heater outlet is set at 190.degree. C..about.230.degree. C. This temperature is set after taking into account factors such as yarn speed, yarn thickness (denier) and heater length. A heater control apparatus is conventionally provided in the draw texturing machine to adjust the heaters to a set temperature. To allow the heater control apparatus to function correctly, the individual heaters and temperature sensors must be paired together correctly.
When, however, a large number of heaters and temperature sensors are wired together, they may be connected so as to be incorrectly paired, causing the incorrectly paired heater to become excessively hot and melt the yarn.
The present invention is provided in view of this problem, and is intended to provide a heater control apparatus that can confirm during initial installation whether the heaters and temperature sensors are correctly paired, and whether the outputs from the temperature sensors are correct.